1. Field of the Invention
The present invention is directed to a transmission for vehicles.
2. Description of the Prior Art
Transmissions for vehicles of the type which are capable of selectively establishing gear ratios for a plural number of forward speeds and one reverse speed by the use of a combination of a torque converter, a planetary gear system and a control mechanism including brakes and clutches are in wide use. Also widely used in such vehicular transmissions is a hydraulic control circuit which distributes operating fluid, of a regulated line pressure from a regulator valve, to the control mechanism by shifting a manual valve to a selected speed range such as forward 1st, forward 2nd, reverse or the like.
With the combination of the control mechanism and the hydraulic control circuit, it is known to provide a D(drive)-range position for the manual valve, controlling the control mechanism to form a gear train of a speed ratio equivalent to that of the low-speed range (e.g., 1st speed) of the manual valve when detected vehicle speed is lower than a predetermined speed and to form a gear train of a speed ratio equivalent to that of the high-speed range (e.g., 2nd speed) of the manual valve when the vehicle speed is higher than the predetermined speed.